Figure



March 10, 1964 FUCHS 3,124,194

AUTOMATIC SAFETY DEVICE FOR FURNACES Filed May 24, 1961 l 5O 54 *5 4o 52 56 1, 5a 52 2,2, s 56 J i a) 55 55a 54 r F1 g.2

b0 62 I R cc E 74 25 28 36 g Y 5 49 i k Q I fie a 24 2o 4* a? 26 INVENTOR ATTORNEY United States Patent Claims The present invention relates to an automatic safety device for a furnace, and more particularly to a safety device for automatically interrupting the operation of a furnace when the same develops smoke or soot due to a lack of sufficient air necessary for a complete combustion.

The present invention is particularly concerned with furnaces of the type in which primary air is supplied to an oil burner, while secondary air is drawn into the combustron chamber mainly by the suction effect produced by the flue draft which at the same time draws the flame gases mto the combustion chamber which is connected with the usual fine draft producing means, e.g. a chimney or a suction fan. The term flame gases is hereinafter employed to designate the mixture of uncombusted oil, primary air and combustion gases which mixture is produced by vaporizatron or atomization of the oil supplied to the burner and its subsequent ignition in an atmosphere of the primary air.

The type of oil furnace with which the invention is particularly concerned is widely used for heating purposes and for boilers, and usually comprises a fire chamber in which the burner is located and through which primary air is blown, and a combustion chamber having an inlet receiving the flame gases from a corresponding outlet opening in the fire charnber. The fire chamber and the combustion chamber are spaced and have confronting walls defining an open space through which secondary air is sucked into the inlet of the combustion chamber. This arrangement is not only very common in oil furnaces, but is of particular advantage if an existing furnace is adapted to be heated by an oil burner.

If an evaporation type oil burner is used, a fan or blower produces the stream of primary air. If an atomizing burner is used, a compressor provides the primary air, In any event, if the means by which the primary air is moved becomes inoperative, for example due to failure of the drive motor or due to a damage to a bearing, incomplete combusion takes place, and smoke and soot develops which passes through the space through which normally secondary air is admitted, so that the surroundings of the furnace, or the entire house, are filled with smoke. Similarly, if the chimney does not operate properly, or if the smoke tubes in the furnace or boiler are clogged by soot, the primary air and the flame gases cannot pass into the combustion chamber, so that smoke and soot passes into the open space through which normally secondary air is admitted to the combustion chamber of the furnace. Clogging of the smoke tubes will very soon take place, if the fan or compressor for primary air breaks down, and in this event the furnace room, or even the entire house, may be filled with smoke before the failure of the fan or compressor for primary air is noted.

It is one object of the present invention to overcome this disadvantage of furnaces of this type, and to provide an automatic safety device which stops the operation of the furnace when smoke or combustion gases escape from the furnace.

Another object of the present invention is to stop the operation of the furnace when smoke or combustion gases enter the open space through which normally secondary air is admitted to the furnace.

Another object of the present invention is to interrupt the operation of the furnace when the temperature in a normally cool region in the proximity of the furnace increases.

Another object of the present invention is to draw at least part of the primary air from an open space through which normally secondary air is admitted, and to provide temperature responsive means which effect stopping of the furnace operation if instead of cool air, hot gases are drawn by the air moving means past the temperature responsive means.

With these objects in view, the present invention mainly relates to an automatic safety device for a furnace. One embodiment of the invention comprises a burner located in the region of the inlet of a combustion chamber which has a chimney or other draft producing means; air moving means, for example a fan or compressor, for moving primary air past the burner and the flame gases produced thereby into the inlet of the combustion chamber; conduit means heated by the burner means, and preferably located outside of the Wall of a fire chamber surrounding the burner; temperature responsive means in the conduit means; and control means for rendering at least the burner, and preferably also the air moving means, inoperative when the temperature responsive means react to an increased temperature.

The draft producing means draw flame gases and a stream of secondary air into the inlet of the combustion chamber. One end of the conduit means is located in the region of the stream of the secondary air, and the other end of the conduit means is located in the region where the air moving means produce suction so that at least part of the primary air is supplied through the conduit means and cools the same.

During the normal operation of the furnace, the heat produced by the burner heats the conduit means, and the air flowing therethrough cools it, so that a normal temperature range is maintained in the conduit means. The temperature responsive means does not react to such normal temperature.

However, if the normal flow of primary air is impaired, for example due to stopping of the air moving means, clogging of the combustion chamber, or insuflicient draft due to weather conditions, no secondary air is drawn toward the inlet of smoke lines of the combustion chamher, but on the contrary hot combustion gases, soot and smoke will fill the space in which normally secondary air flows, and enter the conduit means so that the temperature responsive means responds, and actuates the control means for stopping the supply of oil to the burner, and for stopping the motor of the air moving means.

The temperature responsive means includes a thermocouple, or another sensing means, for example a temperature responsive electric switch, or a bi-metal switch, connected to the circuit of the motor of the air moving means, and to an electromagnetic means which operates a valve in the oil supply conduit for the burner.

The entire primary air may be supplied to the air moving means through the conduit in which the temperature responsive means is located, however, it is preferred to provide another inlet for the primary air so that the conduit means can be dimensioned for only part of the primary air, and is comparatively small to facilitate its mounting in the region of the fire box of the burner.

The conduit means of the temperature responsive means may be placed in the duct for primary air, but is preferably arnanged within a thermo-insulating jacket surrounding the fire chamber and forming with the same duct for primary air.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, to-

gether with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which FIGURE 1 is a longitudinal sectional view of a portion of a furnace provided with the automatic safety device of the present invention, and

FIGURE 2 a detailed sectional view, in a larger scale, of a bi-metal switch used as a sensing means in the automatic safety device according to FIGURE 1.

According to FIGURE 1 the burner part of the furnace comprises a pot-shaped wall 4 open on one side and closed by a cover means 14 which has an outlet means and defines with wall 4, a fire chamber in which the burner 6 is located. Burner 6 is supplied with oil through a supply conduit '7. The fire chamber 1 has inlet means in the form of perforations 3 in wall 4, and is enveloped by a jacket including an inner wall 8, an outer wall 20, and thermo-insulating means 21 between cylindrical portions of wall 8 and of wall 25. Wall 8 has a bottom portion 2 with an opening 13, and wall has a corresponding bottom portion 22 with an opening 23 which is located opposite opening 13.

A motor 12 drives an impeller rotor 11 which is located between wall 4- and wall portion 9, and whose suction portion is located in the opening 13. Upon operation of motor 12, primary air is drawn through opening 23 in the direction of arrow 24 and blown by the discharge portion of rotor 11 into the annular duct it? etween walls 4 and 8 from where the primary air passes through the inlet perforations 3 into the interior of the fire chamber 1 to evaporate the oil supplied to burner 6 so that after ignition combustible burning flame gases pass through outlet means 15 in the direction of the arrow 19 into the inlet 16 into the combustion chamber 18 of the boiler part 5 of the furnace.

The boiler part 5 includes a water chamber 25 surrounding the combustion chamber 13, and a thermoinsulating layer 26. The wall portion 17 of the boiler part 5 confronts the cover wall portion 14 of the burner part 2 and forms with the same an open space 27 of annular shape which gradually widens in outward direction.

The flue draft or chimney draft acting in the boiler part 5 in the direction of the arrow 19 and being produced by the usual flue draft producing means (not shown in the drawing), e.g. a chimney or a suction fan connected with the boiler part, will have a suction effect on the air in the open space 27, so that secondary air is drawn into the open space 27 in the inward direction of arrow 25 and passes through openin 16 into the combustion chamber it; to aid in the complete combustion of the vaporized oil.

A conduit means 25 in the form of a tube passes through the thermo-insulating material 21 between walls 8 and 2t and has one end passing through cover wall means 14 and opening in the open space 27 near the periphery of cover wall 14. The other end of tube 29 opens in the free space between bottom wall portion 9 and bottom wall portion 22 so that during operation of the air moving means 11, primary air is drawn in the direction of the arrow 34 into tube 29 and passes in the direction of arrow 35 through opening 13 to mingle with the primary air entering through opening 23 in the duct If It is evident that the primary air supplied through perforations 3 to burner 6, is partly supplied from the region 36 of the space 2'7 which communicates with the opening 16 of the combustion chamber 18.

In the conduit means 25, and preferably adjacent the region 3% of the open space 27, a temperature-responsive sensing means 32 is located. The temperature-responsive sensing means 32 is constructed as a bi-metal switch according to FIGURE 2 of the drawing, the switch being shown on a larger scale in FIGURE 2.

In FIGURE 2 the bi-rnetal switch is in open position, that is when abnormal temperature occurs in the region of the thermoswitch owing to a failure. During the normal operation of the furnace the bi-metal switch 32 is closed. The bi-metal switch consists substantially of a bi-metal strip 44) which carries on its free end a contact 41 and of a metal contact holder 42 carrying a contact 43 on its free end. The parts 4 0 and 42 are connected by conductor means 33 and 33a which pass outwards through a protecting tube 44 which is held firmly in the bottom portion 22 of the burner part. In the end of the protecting tube located in the conduit means 29 an insulating piece 45 is inserted which insulates the parts 4% and 4-2 from each other and from the protecting tube 44. The same end of the protecting tube also carries a closed housing which surrounds the parts 49 and 42.

When the thermoswitch 32 is in the open position shown in FIGURE 2 it interrupts the connection between the conductor means 52 and a conductor means 54 of the control circuit for a magnetic valve, designated as a whole by 63, and the motor 12.

Any suitable source of current, for example an existing supply network is connected to the conductor means 43 and 49 at St; and 51 respectively.

The conductor means 52 branches from the conductor means 45 and is connected to the conductor means 33 by a push-button cut-off switch 53 which is operated when the operation of the whole furnace is to be stopped. The conductor means 33a is connected by a push-button cut-in switch 57 to the coil of a relay 56 through the intermediary to a conductor means 47. A conductor means 5 5 branches from the conductor means 33a in front of the switch 57 and leads to a holding contact 55 of the relay 56. The other pole of the self-holding contact 55 is connected to the conductor means 47. The second terminal of the coil of the relay 56 is connected to the conductor means 49.

Also coordinated to the relay is a working contact 53 which is located in the conductor means 48 which is one of the feed conductors for the motor 12. The other feed conductor of the motor 12 is the conductor means 49.

Following the relay 56 feed conductors 60 and 61 for the magnet coil 62 of the magnetic valve 63 branch from the conductor means 48 and 4& The housing 64 of this magnetic valve is located in the oil supply conduit 7, the oil entering the housing in the direction of the arrow at 65. At the oil outlet 66 from the housing 64 a valve seat 67 is provided. In the position shown in FIGURE 1 a valve head 68 sits tightly on the valve seat 67 under the pressure exerted by a spring 69, one end of which bears against the head 68 and the other end against the opposite wall of the housing. The valve head is connected to a shaft 70 which extends with close fit through the wall of the housing 64 and carries on its end facing the magnet coil 62 an armature 71 of magnetic material.

In the position shown in FIGURE 1 the coil 62 is deenergized because the connection between the conductor means 52 and the coil of the relay 56 is interrupted by the open bi-metal switch 32 and consequently the relay contact 58 is open. For this reason the motor 12 is switched off.

When the furnace installation is set in operation the temperature at the thermoswitch 32 is so low that the bi-metal strip 40 causes the contact 41 to bear against the contact 43 so that the conductor means 52 is connected with the conductor means 47. Now to start up the installation the push-button cut-in switch 57 is briefly operated with the result that the relay 56 is energized and the two contacts 55 and 58 of the relay are closed. After the cut-in switch 57 is released the coil of the relay 56 is maintained in energized state by the holding contact 55 and the conductor means 54.

Therefore the motor 12 receives current through conductor means 58 and 32 and drives the impeller rotor. At the same time the magnet coil 62 is supplied with current through conductor means 60 and 61 and attracts the armature 71 so that the valve head 68 is lifted against the action of the spring 69 and frees the passage for the oil through the supply conduit 7 through the housing 64 so that the burner 6 is fed with oil.

This working state above described is maintained during the normal operation of the furnace as long as no increase in temperature beyond the normal working temperature occurs at the bi-metal switch 32. If, however, an abnormal increase in temperature takes place in the conduit means 29 in the vicinity of the bi-metal switch 32, due to the reasons indicated above, the bi-metal switch 32 opens and the valve 63 is shifted to the closed position shown in FIGURE 1.

At the same time the motor 12 is switched off by the relay contact 58. The closed position of the valve 63 remains even after decrease of the temperature in the region of the bi-metal switch 32, because the self-holding contact 55 is then broken. Consequently no oil can then enter the switched-off furnace. To start up the furnace installation again after the cause of the breakdown which has automatically effected the switching off of the furnace, has been removed, it is first necessary to again operate the cut-in switch 57.

instead of the bi-metal switch 32 some other temperature-responsive sensing means, for example, a semi-conductor or a thermocouple can be used for the electrical control of the switching operation above described, combined with a suitably constructed amplifying and controlling circuit arrangement for actuating the magnetic valve, and for switching the motor 12 on and off.

instead of a magnetic valve 63 some other valve controlled by the temperature-responsive sensing means 32, for example a float valve, may be used.

Thus the above described furnace operates in the following manner: During normal operation of the furnace, the air moving rotor 11 draws primary air through opening 23 in the direction of the arrow 24, and through conduit means 29 in the direction of the arrows 34 and 3S and discharges the primary air through duct and inlet perforations 3 into the fire chamber 1 so that oil supplied by supply conduit 7 to the pan-type burner 6 is evaporated and ignited and a stream of flame gases consisting of a fuel-air mixture and combustion gases passes in ignited condition in the direction of the arrow 19 through outlet opening 15 and inlet opening 16 into the combustion chamber 18. The flue draft acting in the direction of the arrow 19 draws secondary air in the direction of the arrow 28 and through the space 27 into the inlet 16. The conduit means 29 and 31 are dimensioned so that a substantial portion of the primary air passes through conduit means 29, cooling the thermoresponsive sensing means 32 which is at the same time heated by the heat of the wall 4 which is transferred through wall 8.

During normal operation, the temperature in the conduit means 2? will be approximately 100 C. The temperature of the Wall of conduit means 29 is higher, and would cause sensing means 32 to respond, but the primary air passing in the direction of arrow 34 through conduit means 32 reduces the temperature at the sensing means to 100 C. The thermo-responsive sensing means 32 is designed and selected to respond at a higher temperature of, for example 125 C. Therefore, contacts 41, 43 remain closed, relay 56 and coil 62 are energized, the motor 12 and coil 62 are connected into the circuit.

In the event that the motor 12 stops due to a failure in the power supply, or for any other reason, the air moving rotor 11 will not move any primary air through openin s 23 and 13, and through conduit means 29 into the tire chamber 1 which will result in incomplete combustion and the developing of smoke and soot which will clog the fines of the furnace so that smoke and soot will pass in the direction of arrow 38 through the open space 27 into the room in which the furnace is located.

However, as soon as no primary air is drawn in the direction of the arrows 34 and 35 through conduit means 29, the same will be insufiiciently cooled, and the heat of wall 4 of fire chamber 1 will increase the temperature of the conduit means 29 so that the sensing means 32 is exposed to a temperature above 125, and, for example, a temperature of 150 C. may be reached in the conduit means 29. In this event, the bi-metal strip 40 opens contacts 41, 43, relay winding 56 is disconnected, and contacts 58, 55 open. Motor 12 and coil 62 are disconnected, and spring 69 closes valves 67, 68, stopping the supply of oil through the supply conduits 7 so that the operation of the burner 6 is terminated.

This arrangement operates with a certain delay, so that a momentary interruption of the operation of rotor 11 will not effect the disconnection of the supply of oil to burner 6. This is due to the fact that a certain time after stopping of impeller rotor 11 must pass before the temperature in conduit means 29 increases from C. to C.

In the event that the draft of the chimney of the boiler part 5 is substantailly reduced, or in the event that the smoke tubes are clogged by soot, the safety device of the invention will respond, even if the air moving means 11, 12 continue to operate. The hot gases passing through outiet opening 15 in the direction of the arrow 19 into the combustion chamber 18 cannot pass through the combustion chamber, and consequently move, at least partly, outwardly in the open space 27 toward the region 30 so that instead of fresh secondary air, hot gases are sucked into the conduit means 2 and increase the temperature of the thermoresponsive sensing means 32 until the same respond and operate switch 58 to stop motor 12. This response takes place with very little delay, namely as soon as hot gases reach the region 30, so that almost no smoke will enter the furnace room in the direction of the arrow 38.

It will be appreciated that the opening 23 for the admission of primary air as represented by arrow 24, is not absolutely necessary, and that all primary air can be supplied through an accordingly designed conduit means 29. iowever, the comparatively small conduit means 29 can be advantageously arranged between the outer and inner walls of the jacket and within the insulating layer 21 so that it is mainly cooled by the air passing therethrough, and not by the ambient air.

It will be understood that each of 'the elements described above, or two or more together, may also find a useful application in other types of furnaces differing from the types described above.

While the invention has been illustrated and described as embodied in an automatic safety device for a furnace including a temperature responsive means reacting to a disturbance of the flow of secondary air into the combustion chamber of the furnace, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; burner means in the region of said inlet; air moving means having a suction portion and a discharge portion for moving primary air past said burner means and frame gases produced thereby into said inlet; conduit means located in the proximity of said burner means to be heated by the same, and having one open end disposed in the region of said inlet so as to be located in said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering at least said burner means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means with insufficient draft in said combustion chamber is prevented.

2. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; burner means in the region of said inlet; air moving means having a suction portion and a discharge portion for moving primary air past said burner means and flame gases produced thereby into said inlet; conduit means located in the proximity of said burner means to be heated by the same and having one open end disposed in the region of said inlet spaced a substantial distance from said inlet so as to be located in a cool portion of said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplie through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering said burner means and said air moving means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insufficient draft in said combustion chamber is prevented.

3. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; air moving means having a suction portion and a discharge portion for moving primary air through said inlet means past said burner means, and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located in the region of said fire chamber means to be heated by the same, and having one open end disposed in said open space so as to be located in said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering at least said burner means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insuflicient draft in said combustion chamber is prevented.

4. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having fine draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; air moving means having a suction portion and a discharge portion for moving primary air through said inlet means past said burner means, and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located in the proximity of said fire chamber means to be heated by the same, and having an open end disposed in said open space spaced a substantial distance from said inlet and in the end region of said confronting wall portions so as to be located in a cool portion of said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering at least said burner means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insufiicient draft in said combustion chamher is prevented.

5. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; air moving means having a suction portion and a discharge portion for moving primary air through said inlet means past said burner means, and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located in the proximity of said fire chamber means to be heated by the same, and having one open end disposed in said open space so as to be located in said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering said burner means and said air moving means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insufiicient draft in said combustion chamber is prevented.

6. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having fiue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; an outer jacket having a wall enveloping said fire chamber means spaced from the same so as to define with the same a duct communicating with said inlet means; air moving means having a suction portion and a discharge portion in the region of said duct for moving primary air through said duct and said inlet means past said burner means, and fiame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located outside of said wall of said jacket in the proximity of said fire chamber means to be heated by the same and having one open end disposed in said open space so as to be located in said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of sec ondary air toward said inlet or due to a failure of said air moving means; and control means for rendering at least said burner means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insufiicient draft in said combustion chamber is prevented.

7. An automatic safety device as set forth in claim 6 wherein said outer jacket has an inner wall enveloping said fire chamber means, and an outer wall enveloping said inner wall, and including thermo-insulating means between said outer and inner walls; said conduit means passing through said thermo-insulating means.

8. An automatic safety device as set forth in clairn 6 wherein said fire chamber means and said jacket have confronting walls defining said duct; and wherein said inlet means of said fire chamber means are a plurality of perforations in said wall of said fire chamber means.

9. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; an outer jacket having an inner wall having an opening and enveloping said fire chamber means so as to define with the same a duct communicating with said inlet means and with said opening, and an outer wall having an opening registering with said opening in said inner wall; air moving means including a rotor at least partly located in said duct and having a suction portion in the region of said openings in said inner and outer walls and a discharge portion for moving primary air entering through said openings through said duct and said inlet means past said burner means, and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located between said inner and outer walls in the proximity of said fire chamber means to be heated by the same and having one open end disposed in said open space so as to be located in said stream of secondary air and another open end communicating through said opening in said inner wall with said suction portion so that part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering at least said burner means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insuificient draft in said combustion chamber is prevented.

10. An automatic safety device as set forth in claim 9 and including thermo-insulating means between said inner wall of said jacket and said conduit means.

11. An automatic safety device as set forth in claim 9 wherein said temperature responsive means includes a temperature responsive sensing means located near said one end of said conduit means, and connecting means connecting said sensing means with said control means and passing through said other end of said conduit means and through said outer wall of said jacket.

12. An automatic safety device as set forth in claim 9 wherein said confronting wall portion of said fire chamber means is a cover means closing said fire chamber means, said duct, and the space between said outer and inner walls of said jacket, said cover means having an outlet opening aligned with said burner means and registering with said inlet of said combustion chamber means, said cover means having an opening near the outer periphery thereof through which said conduit means passes so that said one end of said conduit means is located in said open space, said open space defined by said cover means and by said wall portion of said combustion chamber means being annular and surrounding said inlet of said combustion chamber.

13. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communiacting with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; an outer jacket having a wall enveloping said fire chamber means spaced from the same so as to define with the same a duct communicating with said inlet means; air moving means having a suction portion and a discharge portion in the region of said duct for moving primary air through said duct and said inlet means past said burner means, and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located outside of said wall of said jacket in the proximity of said free chamber means to be heated by the same and having one open end disposed in said open space spaced a substantial distance from said inlet and in the end region of said confronting wall portions so as to be located in a cool portion of said stream of secondary air and another open end located in the region of said suction portion so that at least part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal opera tion of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering said burner means and said air moving means inoperative when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insuficient draft in said combustion chamber is prevented.

14. An automatic safety device for furnaces, comprising, in combination, combustion chamber means having flue draft producing means and an inlet so that a stream of secondary air is drawn into said inlet by the flue draft; fire chamber means having inlet means and outlet means located opposite said inlet of said combustion chamber means, said fire chamber means and said combustion chamber means having confronting wall portions defining an open space communicating with said inlet of said combustion chamber means so that secondary air passes through said open space to said inlet; burner means located in said fire chamber; an outer jacket having an inner wall having an opening and enveloping said fire chamber means so as to define with the same a duct communicating with said inlet means and with said opening and an outer wall having an opening registering with said opening in said inner wall; air moving means including an electric motor, and a rotor at least partly located in said duct and having a suction portion in the region of said openings in said inner and outer walls and a discharge portion for moving primary air entering through said openings through said duct, said inlet means, past said burner means and flame gases produced thereby through said outlet means of said fire chamber means into said inlet of said combustion chamber means; conduit means located between said inner and outer walls in the proximity of said fire chamber means to be heated by the same and having one open end disposed in said open space so as to be located in said stream of secondary air and another open end communicating through said opening in said inner wall with said suction portion so that part of the primary air is supplied through said conduit means thereby cooling the latter whereby a normal temperature range is maintained in said conduit means during normal operation of the furnace; temperature responsive means located in said conduit means and adapted to be actuated when the temperature in said conduit means exceeds said normal temperature range due to a disturbance of said stream of secondary air toward said inlet or due to a failure of said air moving means; and control means for rendering said burner means inoperative by interrupting the supply of oil to the same and for rendering said air moving means inoperative by interrupting the circuit of the motor thereof when said temperature responsive means is actuated whereby operation of the furnace after stopping of said air moving means or with insufiicient draft in said combustion chamber is prevented.

15. An automatic safety device for furnaces as set forth in claim 1 wherein said control means include valve means for controlling the flow of fuel to said burner means, an electromagnetic coil for operating said valve means, and a relay having a contact connected in series with said coil; and wherein said temperature responsive means includes a temperature responsive switch con nected into the circuit of said relay and effecting in actuated condition closing of said valve means.

16. An automatic safety device as set forth in claim 15 and including spring means biasing said valve means to close, said coil, when energized effecting opening of said valve means; and wherein said heat responsive switch is normally closed so that said relay is energized, and said contact is closed to energize said coil, Whereas when said temperature responsive switch is actuated and opens, said relay is tie-energized, said contact opens, said coil is de-energized, and said spring means close said valve means.

17. An automatic safety device for furnaces as set forth in claim 16 wherein said air moving means includes an electric motor and an air moving rotor, said electric motor being connected in series with said contact so as to be disconnected when said temperature responsive switch opens and effects opening of said contact.

18. A safety device as set forth in claim 16 and including a manually operated start switch connected into the circuit of said relay between the same and said temperature responsive switch, and a holding contact operated by said relay for holding the same energized after release and opening of said manually operated switch.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN AUTOMATIC SAFETY DEVICE FOR FURNACES, COMPRISING, IN COMBINATION, COMBUSTION CHAMBER MEANS HAVING FLUE DRAFT PRODUCING MEANS AND AN INLET SO THAT A STREAM OF SECONDARY AIR IS DRAWN INTO SAID INLET BY THE FLUE DRAFT; BURNER MEANS IN THE REGION OF SAID INLET; AIR MOVING MEANS HAVING A SUCTION PORTION AND A DISCHARGE PORTION FOR MOVING PRIMARY AIR PAST SAID BURNER MEANS AND FLAME GASES PRODUCED THEREBY INTO SAID INLET; CONDUIT MEANS LOCATED IN THE PROXIMITY OF SAID BURNER MEANS TO BE HEATED BY THE SAME, AND HAVING ONE OPEN END DISPOSED IN THE REGION OF SAID INLET SO AS TO BE LOCATED IN SAID STREAM OF SECONDARY AIR AND ANOTHER OPEN END LOCATED IN THE REGION OF SAID SUCTION PORTION SO THAT AT LEAST PART OF THE PRIMARY AIR IS SUPPLIED THROUGH SAID CONDUIT MEANS 